System of distribution



I E. F. w. ALEXANDERSON ,835,131

SYSTEM OF DISTRIBUTION Filed May 22, 1923 3 Sheets-Sheet l Inventor' Ernst F: \X/. Alexander-son, y I

His Attorney.

3 E. F. w. ALEXANDERSON 1,835,131

SYSTEM OF DISTRIBUTION Filed May 22, 1923 3 Sheets-Sheet 2 33 74 5;: Fig.2.

InVenbor- Ernst F1 \X Ale'xand'erson,

y 2%...23 His Atterney.

Dec. 8, 1931. E. F. w. ALEXANDERSON 1,835,131

SYSTEM OF DI STRIBUTION Filed May 22, 1925 3 Sheets-Sheet 5 IPA/enter 3 Ernst F \X/. Alexander'son,

YXW ,1

His Attorney.

Patented Dec. 8, 1931 UNITED STATESPATENT oFFic-E Inner r. w. amxmxasox, or scnmwcranr, mew YORK, assnmon. 'ro damn.

a aLEc'rmc company, a conroaa'rron or NEW YORK sYsrm or msrmurron Application fled Kay 22, 1928. Serial Ne. 640,725.

My present invention relates to systems of electrical distribution, and more partlcularl to systems for supplying current from a direct current distribution system for the operation of alternatingcurrent consumption ap aratus.

ne of the objects of my invention is to provide a simple, reliable and. efficient apparatus for converting direct current to alterdistribution systems.

In carrying my invention into effect, I provide a plurality of transformer windings and supply current from the direct current source to the primary windings through a plurality of electron discharge valves. In order that these valves should operate at the best efiiciency they should be controlled in such a way that current will flow only when the potential difference between the terminals is comparatively small and substantially the maximum current carried by the valve should be permitted to flow therethrough during the entire period during. which the valve is rendered conducting.

Still another object of my invention is to provide an apparatus for controlling the flow of current throu h the valves which will renfrom a'sine wave becoming substantially rectangitlar. This will result in the production in the secondary windings of the transformer ,of waves having pronounced harmonics,

which in some cases maybe objectionable.

Still another object'of in invention is to provide an apparatus where y the objectionable harmonics in the secondary current will be largely eliminated. V

Thenovel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further ob'ects-and advantages thereof, will best be an erstood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 shows diagrammatically one organization of apparatus whereb my inven-' tion may be carried into effect; Figs. 2 and 3 show modifications in the apparatus and connections used for controlling the operation of the'valves; and Figs. 4 and 5 are oscillograms showing the wave form of the current obtained with different connections of the apparatus.

' I have indicated in Fig. 1 a plurality of.

electron discharge valves 1 'to 12, inclusive,.

for supplying current from the direct current distribution mains 13 and 14, to the primary windings 15 to 26, inclusive, of twothree-phase transformers 27 and 28. The

primaries of each transformer are connected in double Y with interphase transformers 29 and 30 between the two neutrals for maintaining a proper balance between the currents supplied to the two primaries. The secondary windings 31 of transformer 27 are connected in delta and the secondary windin 32 of transformer 28 are connected in Y in order that the. primary terminal voltages of one transformer may be displaced by thirty degrees from the terminal voltages of the other and the secondary volta 'es may be in phase for reasons which will be more fully explained later. I This combination gives the equivalent of twelve phases for the primaries and the use of this large number of phases in combination with other expedients provided gives a substantially sine wave form of current in the alternatingcurrent mains 33, 34

and 35*even though the current supplied to each primary winding departs materially from the sine wave form. Windings 36, 37 and 38 which are. wound on the same cores as the secondary windings of transformer 28, as indicated and connected together in delta also improvethe wave form by furnishin a short circuit path for all harmonics divisi 10 by three. 1

The valves 1 to 12 are indicated as bein of the three electrode type having the usua cathode 39, anode 40 and discharge controlling grid 41. These may be of the high vacuum thermionic type or may operate by gas ionization. In order to secure the desired efliciency in operation these valves should be made conducting during approximately onethird .of each cycle. The positive potential applied to the grids to render the valvesconducting should also be impressed in such a way that the current through the valve may quickly build up to its maximum value. 1 In order that commutation may be effected without setting up surges in the system the valves should also be rendered non-conducting at .instants when the current therethrough has fallen to zero or substantially zero.

To secure these results substantially rectangular potential Waves should be applied to the controlling grids of the valves if the valves are of the thermionic type. If the valves are of the ionization type all that is necessary is to supply to the grlds a positive potential of short duration to permit the cur- 'rent to start. In order to secure the desired potential waves for controlling the valves a series of high potential, low power threeelectrode thermionic valves 42 to 53 inclusive, may be employed: The anodes of these valves are connected to the positive side of the direct current supply by means of the lead 54 through individual resistances 55.

The controlling potentials for the gridsof valves 42 to 53 are obtained from the alter: nating current distribution mains through conductors'56, 57 and 58, which are connect ed to equidistant points in the ring winding 59. The grids of the valves 42 to 53, are conn'ected by adjustable taps 60 to the ring wind ing 59 and b suitable adjustment of these taps potentia s of the desired-phase may be obtained. The grid circuits of valves 42 to 53 may be completed through a winding 61, the middle point 62 of which is connected to the cathodes of the valves through a grid biasing battery 63.

' The anodes of valves '42 to 53 are connected through condensers 64 to the primaries of transformers 65, the secondaries of which are connected in the grid circuits of valves 1 to 12. When the valves 42 to 53 are norr-conducting their anodes will be at substantially the same potential as the positive side of the direct current supply. The charging current of condensers 64 will then induce in the secondaries of transformers 65 a current which will make the grids 41'negative and prevent the flow of current through valves 1 to 12. As soon as valves 42 to 53.

' have been rendered conducting their imformers 65 will reverse, causing grids 41 to to the grids of valves 42 to 53, the duration the impedance of the valves from a maximum to a minimum value. will be much less than the time, during which it is desired that cur-,

rent shall flow in valves 1 to 12.. By this ex- ,pedient substantially rectangular current waves may be set up in valves 42'to 53 and substantially rectangular potential waves apbe so chosen that the time required to change plied to the grids of valves 1 to 12. How-- I ever, I do not claim broadly as my invention I the feature of supplying the grids of electricvalves with rectangular potential waves to increase the efficiency of the valves, for this feature is disclosed and broadly claimed in '7 I a copending application of Louis A. Hazeltine, S. N. 341,150, filed November 28, 1919. proper choice of the potentials applied of the positive potential wave applied to the grids of valves 1 to 12 may be made equalto the time during which it is desired to have current flow in valves 1 to 12. By suitable adjustment of the taps 60 the instants when thepotentials applied to the grids of valves I 1 to 12 change from negative to positive may be made to correspond to the instants when it is desired that the currents should .begin to flow in valves 1 to 12. The potentials'ap-, pliedto the grids of valves 42 to '53 should lead the secondary potentials produced in the transformers in orderxthat each of the valves 1 to 12 may be rendered conducting before current in the preceding valve has fallen-to zero. By this provision the current will be.

permitted to build up in one valve during the time it is dying down in the preceding valve and the current supplied to each half of V the-primary windings will be tially constant.

- Any convenient form of frequency determinin element may be connected to the alternatmg current, distribution system for fixing the frequency of the alternating currents produced. In the system illustrated a rotary converter 66 is connected to the alternating current distribution system and the speed at which the converter is operated may 'determine the frequency of the alternating currents produced. This converter may be kept substanused to charge a storage battery 67 for supplying low voltage direct current for any desired purpose, as for example, for heating the cathodes of valves 42 to 53. The operation of the system described may be initiated by starting the rotary converter 66 by means of current from the storage battery 67 In the system shown in Fig. 1, four of'thevalves will be carrying current at any given instant and a change in admission of current from one valve to a succeeding valve will take place every thirty time degrees' The periods during which the different valves placed in will be carrying current and the changes during a complete cycle will be as follows a) 00 90" 120 150' 100' 210 240 27o m 330? 1 1 1 1 2 2 2 2 a a 3 a a o o a o 4 4 4' 4 a 5 s o 1 7 7 1 a sa a a a a 11 11 11 12 12 12 12 1o "10 1o 11.

while the'fifth and seventh harmonics in the secondaries of the two transformers will be 180 out of phase and will therefore be short circuited in the secondary windings and will not be supplied to the load circuit if the load is equally divided between the two transformers. The improvement in wave form obtained in this way is illustrated by the oscillograms of F igs. 4 and 5, Fig. 4 showing the wave form 0 current obtained from one set of'transformers alone, and, Fig. 5 showing the wave form of the current obtained when the two sets of transformers are operating together as described.

In Fig. 2 I have indicated, a modified arrangement for securing the desired control of the current through the main valves. In this case the potentials for controlling the grids densers 64 discharge through resistances 69 til rangement as well as of auxiliary valves 42 to 47 are obtained by means'of a transformer having its primary windings connected in extended delta in order to obtain the desired phase relation of the grid potentials, andhaving a star tonnected secondary. The valves 42 to 47 are shunted by resistances 69 so that when the valves are non-conducting the potential applied to the condensers 64' is of a value intermediate the potentials of the opposite sides of the direct current supply. The condensers 64 will then become charged making the grids of valves 1 to 6 positive and permitting current to flow. When the valves are made conducting the potentials of the anodes of valves 42 to 47 are greatly reduced and the conand 70 causing the grids of valves 1 to 6 to become negative and prevent current from flowing. Current limiting resistances 71 are preferably inserted in the grid circuits of ing potentials for the grids of the different valves may be employed if necessary to assist in obtaining the desired action in this arin the system shown in Fig. 1.

In this case I have indicated the valves 1 to 6 as being of the thermionic type and the cathodes of all of the valves are heated from the alternating current distribution system 72.- While in Fig. six-phase system, equally applicable base-system of Fig. 1. have indicated .a connection by means of a transformer 2 I have indicated only a the arran ement shown is to the twe ve- In Fig. 3

' whereby mercury or other forms of rectifier may be used for obtaining the desired rectangular potential wave for controlling the operation of valves 1 to .12. In this case a full wave rectifier 73 is connected by means of the transformer 7 4 across one phase of the alter nating current distribution systems The.

primary windings 75 and 76 of transformers 77 and 78 are connected in shunt to the cathodeand anodesofrecti-fier 73. When either side of the rectifier is not in operation the grid ofthe valve which is connected to 5 the correspondin secondary of transformers 7.7 and 78 ismade negative. As soon as the resistance between the cathode and either. anode ofthe rectifier is broken down and current begins to flow the'grid ing valve is made positive permitting current to flow. This change in potential is produced quickly and the ositiveipotential wave applied to the grids of tially rectangular. I have indicated only one iectifier, but it will be understood that a rectifier will be required for each of the three 1 phases of the alternatingcurrent distribution system. n What I claim as new and desire to secure by Letters Patent of the United States is 1. The combination in a system of electrical distribution of a source, of direct current, a plurality of primary transformer windings connected to said source through a plurality of valves, a plurality of secondary trans-' former windings inductively related to said primary windings and connected to a consumption circuit, andmeans comprising electron discharge apparatus for rendering each of said valves non-conducting at times when the current therethrough has become sub stantiallyzero. I 2. The combination in a system of electrical of the-correspondthe valves is substandistribution of a source of direct current, a

sumption circuit, and means comprising elec-- tron discharge apparatus for automatically rendering each of said valves non-conducting at times when the current therethrough has become substantially zero.

3. The combinationin a system of electrical distribution of a source of direct current, a

plurality of primary transformer windings connected to said source through a plurality ofvalves, aplurality of secondary transformer windings inductively related to said primary winding and connected to a consumption circuit, and means connected to the consumption circuit for vrendering each of said valves non-conducting at times when the current therethrough has become substantially zero.

4. The combination in a system of electrical distribution of a source of direct current, two

pairs of three-phase primary transformer windings connected to said source through a plurality of valves, a three-phase secondary transformer winding associated with each pair of primary windings, said secondary windings being connected to a three-phase distribution circuit, and means for regulating the supply of current from said direct current source to said transformer windings in such a way as to supply to one pair of rimary windings currents slightly displace in phase from those supplied to the other pair of primary-windings.

5. The combination in a system of electrical distribution of a source of direct current, a plurality of primary transformer windings connected to said source through a plurality of valves, a plurality of secondary transformer windings inductively related "to said primary windings, and connected to a consumption circuit, and means comprising electron discharge apparatus for supplying to said primary windings substantially rectangular current waves.

6. The combination in a system of electrical distribution of a source of direct current, a plurality of primary transformer windings connected to said source through a plurality of valves, a plurality of secondary transformer windings inductively related to said primary windings and connected to a consumption circuit, and means comprising electron discharge apparatus for controlling the action of the valves to supply to said primary windings substantially rectangular current waves.

7 The combination in a system of electrical distribution of a source of direct current. a plurality of primary transformer windings connected to said source through a plurality of valves, a plurality of secondary Y transformer windings inductively related to said primary windings and connected to a consumption circuit, and means connected to the consumption circuit for controlling the action of the valves to supply in regular succession to said primary windings substantially rectangular current waves.

8. The combination 1n a' system of electrical distribution of a source of direct current,

a plurality vof primary transformer wind-- ings connected to said source through a plurality of valves, a plurality of secondary transformer windings inductively related to said primary windings and connected to a consumption circuit, means for controlling the flow of current through said valves, and electron discharge means forsupplying to said controlling means substantially rectan-' gular potential waves.

9. The combination in a system of electrical distribution of a source of direct current, a plurality of-primary transformer windings connected to saidsource through a plurality of valves, a plurality of secondary; transformer windings inductively related to said primary windings and connected to a consumption circuit, means for controlling the fiow of current through said valves, and electron discharge means, for supplying in regu- =lar succession to the rcontrolling means of said valves substantially rectangular potential waves.

10. The combination in a system of electrical distribution of a source of direct current, a plurality of primary transformer windings connected to said source through a plurality of valves, a plurality of secondary transformer windings inductively related to said primary windings and connected to a consumption circuit, means for supplying to said primary windings substantially rectangular current waves, and means for eliminating harmonics produced in the secondary windings. I

11. The combination in a system of electrical distribution of a source of direct current, a plurality of primary transformer windings connected to said source through a plurality-of valves, a plurality of secondary transformer windings inductively related to 1.

said primary windings and connected to a consumption circuit, means for controlling V the action of the valves to supply to said primary windings substantially rectangular".

current waves, and means for eliminating harmonies produced in the secondary wind ings.

12. The combination in a system of electrical distribution of a source of direct current,

a plurality of primary transformer windings connected to said source through a plurality of valves, a plurality of secondary transformer windings inductively related to said primary windings'and connected to a conv sumption circuit, means for controlling the action of the valves to supply in regular succession to said primary windings substantial- 1y rectangular current waves, and means for eliminating harmonics produced in the secondary windings.

13. In combination asource of direct'current, a valve connected thereto, said valve comprising an anode, a cathodeand a grid member, a consumption circuit supplied with current impulses from said valve, and means comprising an alternating current source of ower and a ring winding for impressing on the grld member of the valve an alternating potential of such value that the impedance of the valve is reduced from a maxlmum' to a minimum in a time which is short compared lac with the time during which a current impulse is supplied by the valve. i

14. In combination a source'of direct current, a valve connected thereto, said valve comprising an anode, a cathode and a grid 7 member, a consumption circuit supplied with current impulses from said valve andmeans' comprising an alternating current source of power and a ring winding for impressing on the'grid member of the valve an alternating potential of such value that the'impedance of the valve is reduced from a maximum to a minimumin a time which is short com pared with the time of a halt cycle of the 15 alternating potential.

' 15. In combination a source-of direct ourrent, a valve connected thereto, said valve comprising an anode, a cathode and a grid member, a consumption circuit supplied with current impulses from said valve, means comrising a source of alternating electromotive orce and a ring winding for starting and stopping the flow of current throu h 'said valve and for impressing on the gri mem- I ber of the valve. 'a potential of such value thatthe impedance is reduced from amaximum to a minimum in a time which is short compared with the time during which a current 1m ulse is supplied-b the valve. r n-witness whereo I have hereunto set i my hand this 21st-day of May, 1923.

ERNST F. W. ALEXANDERwN. 

